1. Field of the Invention
The present invention relates to an imaging apparatus, and more particularly, to flash control in flash imaging.
2. Description of the Related Art
In a conventional imaging apparatus, in order to perform successful imaging, an object is generally illuminated with an auxiliary light source such as an illumination device (flash device) when the luminance of the object (hereafter referred to as “object luminance”) is low. A technique for performing automatic flash control of the auxiliary light source, such as a flash device, according to an imaging condition, such as the object luminance, is also known.
For example, Japanese Patent Application Laid-Open No. 2005-204120 discuses a technique for performing gain (sensitivity) control of an imaging apparatus and automatic flash control of a flash unit according to an object luminance. Japanese Patent Application Laid-Open No. 2005-181355 discusses a technique for obtaining information relating to a, so-called, depth of an object (an object distance) from a focus detection result of a focus detection unit having a plurality of focus detection points when flash imaging is performed, to control a shutter speed at the time of the flash imaging.
In the technique discussed in Japanese Patent Application Laid-Open No. 2005-204120, imaging is performed with the imaging gain set low when the object luminance is sufficiently high, and is raised and is maintained, so that a shutter speed takes a predetermined value, when the object luminance is low and the shutter speed takes the predetermined value or less if the imaging gain remains low. When the object luminance becomes lower, so that the required imaging gain exceeds its upper limit, flash imaging is performed.
However, in flash imaging, only objects that are located at the same distance from the flash device are properly exposed. Therefore, in the technique discussed in Japanese Patent Application Laid-Open No. 2005-204120, when objects that differ in object distances exist in a imaging plane at the time of flash imaging, the object at the longer distance becomes dark due to lack of light if an amount of flash is controlled so that the object at the shorter distance is properly exposed.
If the color temperature difference between background light and flash light is large, white balance control is performed with emphasis on the object at the shorter distance so that the object at the longer distance not only becomes dark but also becomes unnatural in color reproduction. Therefore, it is difficult to obtain a good image of each of the objects that differ in object distance.
In the technique discussed in Japanese Patent Application laid-Open No. 2005-181355, the shutter speed at the time of flash imaging is set lower when the depth of the object is determined to be large than when the depth of the object is determined to be small from the focus detection result of the focus detection unit having the plurality of focus detection points. Thus, an amount of exposure to background light is increased so that darkness of the object at the longer distance can be alleviated.
However, generally the shutter speed at the time of flash imaging has already been set to a minimum speed at which camera shake does not affect the captured image. However, when the shutter speed is reduced camera shake can easily affect the image so that it is difficult to obtain a good image without image blur.